Hebei Key Laboratory of Optic-Electronic Information Materials, College of Physics Science and Technology, Hebei University , Baoding 071002, P. R. China.
ACS Appl Mater Interfaces. 2017 Aug 30;9(34):28828-28837. doi: 10.1021/acsami.7b09253. Epub 2017 Aug 17.
Recent years have seen a rapid progress in the power conversion efficiencies (PCEs) of non-fullerene polymer solar cells (NF PSCs). However, the donor materials accordingly used are typical low or medium band gap polymers, some of which possess badly overlapped absorption spectra relative to the low band gap n-type acceptors, for example, 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)indanone)-5,5,11,11-tetrakis(4-hexylphenyl)dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene) (ITIC). To obtain polymers simultaneously owning a wide band gap, a highly extended π-conjugation system, and a low-lying highest occupied molecular orbital (HOMO), a polymer (PBDTSi-TA) incorporating 2-(triisopropylsilylethynyl)thiophene substituted benzodithiophene (BDTSi) and fluorinated benzotriazole (FTAZ) units was designed and synthesized. PBDTSi-TA (E = 1.92 eV) exhibits strong molecular aggregation properties and a lower-lying HOMO energy level compared to its structural analogues. When blended with ITIC and after device optimization with solvent vapor annealing in combination with a developed PDIN/BCP/Ag cathode structure, PSCs yielded a PCE of 7.51%, with V = 0.96 V. Moreover, a rather small energy loss (E) of 0.6-0.63 eV was determined. For comparison, another polymer (PBDTSi-Qx) with a more-electron-deficient quinoxaline-based acceptor unit was also synthesized and applied to NF PSCs. Charge generation rate, exciton dissociation probabilities, dark leakage current, nanoscale morphology, and charge carrier mobilities have been evaluated to probe the reasons for the differentiated performances. The results suggest that PBDTSi-TA is a promising donor material for NF PSCs, and the molecular design strategy demonstrated here would be helpful for pursuing high-performance polymers for PSCs.
近年来，非富勒烯聚合物太阳能电池（NF PSCs）的功率转换效率（PCE）取得了快速进展。然而，相应使用的供体材料通常是典型的低或中带隙聚合物，其中一些与低带隙 n 型受体相比具有严重重叠的吸收光谱，例如 3,9-双（2-亚甲基-（3-（1,1-二氰基亚甲基）茚酮）-5,5,11,11-四（4-己基苯基）二噻吩[2,3-d:2',3'-d']-并吲哚[1,2-b:5,6-b']二噻吩）（ITIC）。为了获得同时具有宽带隙、高度扩展的π共轭体系和低的最高占据分子轨道（HOMO）的聚合物，设计并合成了一种含有 2-（三异丙基硅基乙炔基）噻吩取代的苯并二噻吩（BDTSi）和氟化苯并三唑（FTAZ）单元的聚合物（PBDTSi-TA）。与结构类似物相比，PBDTSi-TA（E = 1.92 eV）具有较强的分子聚集特性和较低的 HOMO 能级。当与 ITIC 共混并通过溶剂蒸气退火与开发的 PDIN/BCP/Ag 阴极结构相结合进行器件优化后，PSC 的 PCE 达到 7.51%，V = 0.96 V。此外，确定了相当小的能量损耗（E）为 0.6-0.63 eV。相比之下，还合成了另一种具有更缺电子喹喔啉基受体单元的聚合物（PBDTSi-Qx），并将其应用于 NF PSCs。已经评估了电荷产生速率、激子解离概率、暗漏电流、纳米级形貌和载流子迁移率，以探究性能差异的原因。结果表明，PBDTSi-TA 是 NF PSCs 的一种有前途的供体材料，这里展示的分子设计策略将有助于寻找用于 PSCs 的高性能聚合物。
